The objective of this study is to characterize quantitatively the processes underlying the generation of action potentials in vertebrte motoneurons and to explore the regulation of those processes. We are using bot isolated spinal cord preparations (frog and rat pinal cord) and rat spinal cord cells grown in tissue culture. Voltage clamp and pharmacological techniques are used to separate the currents that contribute to action potential generation, and to measure the kinetic and voltage dependent properties of those currents. BIBLIOGRAPHIC REFEENCES: E.F. Barrett & J.N. Barrett. Separation of two voltage-sensitive potassium currents, and demonstration of a tetrodotoxin-resistant calcium current in frog motoneurons. J. Physiol. 37 pp. 1976, in press.